Stabilizing fin system

ABSTRACT

A stabilizing fin for damping the rolling motion of a ship and which extends and stows athwartship. The stabilizing fin is rotatably mounted on a fin support axle which is slidably mounted in a fin chamber located athwartship in a ship&#39;&#39;s hull. The stabilizing fin is extended into its operative position and retracted into its inoperative position by a threaded shaft cooperating with a nut mounted to the fin support axle. When in operative position, the stabilizing fin is tilted by actuation of a cam which imparts rotary motion to a fin tilting arm attached to the stabilizing fin. The stabilizing fin is extended, retracted, and tilted by means of hydraulic actuators. The hydraulic system for supplying hydraulic fluid to the hydraulic actuator for extending and retracting the stabilizing fin includes solenoid-operated and pilot-operated valves such that the hydraulic actuator is only supplied with pressurized fluid when the stabilizing fin is properly positioned for fin extension and retraction. The hydraulic system for supplying hydraulic fluid to the hydraulic actuator for tilting the stabilizing fin includes servo and pilot-operated valves such that the hydraulic actuator is only supplied with pressurized fluid when the stabilizing fin is in the fully extended position. A novel servo valve for use in the hydraulic system for controlling the supply of hydraulic fluid to the hydraulic actuator for tilting the stabilizing fin is also disclosed.

United States Patent 1191 Napolitano Dec. 9, 1975 1 STABILIZING FIN SYSTEM [75] Inventor: Pellegrino E. Napolitano, Brooklyn,

[73] Assignee: Flume Stabilization Systems, Inc.,

Hoboken, NJ.

[22] Filed: Aug 18, 1972 [21] Appl. No.: 281,953

Primary ExaminerTrygve M. Blix Assistant Examiner-Charles E. Frankfort Attorney, Agent, or FirmFleit & Jacobson [57] ABSTRACT A stabilizing fin for damping the rolling motion of a ship and which extends and stows athwartship. The stabilizing fin is rotatably mounted on a fin support axle which is slidably mounted in a fin chamber located athwartship in a ships hull. The stabilizing fin is extended into its operative position and retracted into its inoperative position by a threaded shaft cooperating with a nut mounted to the fin support axle. When in operative position, the stabilizing fin is tilted by actuation of a cam which imparts rotary motion to a fin tilting arm attached to the stabilizing fin.

The stabilizing fin is extended, retracted, and tilted by means of hydraulic actuators. The hydraulic system for supplying hydraulic fluid to the hydraulic actuator for extending and retracting the stabilizing fin includes solenoid-operated and pilot-operated valves such that the hydraulic actuator is only supplied with pressurized fluid when the stabilizing fin is properly positioned for fin extension and retraction. The hydraulic system for supplying hydraulic fluid to the hydraulic actuator for tilting the stabilizing fin includes servo and pilot-operated valves such that the hydraulic actuator is only supplied with pressurized fluid when the stabilizing fin is in the fully extended position. A novel servo valve for use in the hydraulic system for controlling the supply of hydraulic fluid to the hydraulic actuator for tilting the stabilizing fin is also disclosed.

50 Claims, 12 Drawing Figures US. Patent Dec. 9 1975 Sheet2of7 3,924,555

U.S. Patent Dec. 9 1975 Sheet 3 of7 3,924,555

bmxmu why US. Patent Dec. 9 1975 Sheet4 0f7 3,924,555

US. Patent Dec. 9 1975 Sheet5 0f7 3,924,555

US. Patent Dec.91975 Sheet60f7 3,924,555

sm/eeoew n/v US. Patent Dec. 9 1975 Sheet 7 of7 3,924,555

Mwtii STABILIZING FIN SYSTEM BACKGROUND OF THE INVENTION The operation of a conventional fin stabilizer for damping the rolling motion of a ship is as follows. A pair of fins is fitted below the water line on each side of the hull amidship, and control drive systems are located within the hull of the ship. The standard control unit senses roll angle and rate of roll, and sometimes roll acceleration as well. The data received by the control unit is evaluated by a computer and an actuation signal is transmitted to the prime movers which orient the fins so that the stabilizing moment produced by the water flow around the fins compensates for the disturbing moments of the waves. The ships rolling motion is thereby damped. The stabilizing fins remain fully extended when in use and are rotated about substantially horizontal axes, oppositely but in unison, thereby changing their angles of encounter with the waves in accordance with the stabilizing moment required. Often these fins are provided with tail flaps so as to increase the moment which can be developed.

Stabilizing fins may be divided into two broad classifications: non-retractable and retractable. Retractable fins may be further divided into two classes, those which extend and stow athwartship, and those which hinge into a fore and aft stowed position and are extended by swinging out into an athwartship position.

Extension and retraction of fins which extend and stowe athwartship are usually performed hydraulically since the diameter of the fin support shaft is such that it may be bored out, as a cylinder, to contain a piston and a piston rod which passes through a stuffing box at the inboard end of the support shaft. Particular disadvantages associated With hydraulic extension and retraction of stabilizing fins include the necessity for isolating the bore of the fin support shaft from the water surrounding the fin, and the difficulty in lubricating and repairing bearings located in the bore.

Stabilizing fin extension and retraction have also been accomplished by meansof a threaded shaft cooperating with a nut-like part of a traverse which carries the fin and which slides on tracks or rails located athwartship in the fin chamber. A particular disadvantage of this arrangement, which is shown in British Pat. No. 888,452, resides in the twisting moment which is exerted on the stabilizing fin and which resists the easy movement of the fin along its major axis. A further disadvantage of this arrangement is the necessity of providing a support means, usually fixed to the fin chamber, for supporting the outboard end of the fin retraction shaft.

Fin tilting has been accomplished in a variety of ways and it is customary to use a hydraulic system for tilting the fin. An illustrative fin tilting arrangement is one in which the fin is rigidly mounted to the fin support shaft which is hydraulically rotated to tilt the fin.

Retractable fins which extend and stow athwartship are generally mounted on guiderails in fin chambers that are mounted on each side of the hull amidship. The prime movers which extend and retract the fins and orient the fins so that the fins compensate for the disturbing moments of the waves are typically located on a deck within the hull of the ship. The drive shafts for the fins pass through stuffing boxes at the inboard end of the fin chambers and must there be properly aligned with the drive shafts for the prime movers which are mounted on the deck of the ship. Since the fin chambers and prime movers are large, bulky pieces of equipment, it is particularly difficult to properly align the respective drive shafts.

As previously stated, retractable fins which extend and stow athwartship are generally mounted on guiderails in a fin chamber. The guiderails are usually positioned in the fin chamber by being attached to a support, typically the flange of a box girder, which is attached to the fin chamber. The guiderails and supports are several feet in length and must be properly leveled if the stabilizing fin is to extend and retract smoothly. In leveling the guiderails, it is customary to properly align the guiderail support in the fin chamber and then machine the mating surface of the support, such as the flange of the box girder, to form as smooth and level a surface as possible. The same machining procedure is employed with respect to the mating surface of the guiderail. After the guiderail is placed on the support with their machined surfaces in abutting relationship, metal shims are inserted between the guiderail and support to make last-minute leveling adjustments and the guiderail and support are then bolted together. This procedure has the particular disadvantage of requiring considerable labor in machining the metal surfaces and raising and lowering the guiderail with shims to level its glide surface.

When hydraulic prime movers are employed to operate stabilizing fins, a hydraulic fluid supply system is required to supply the prime movers with pressurized hydraulic fluid. The electrical input for actuating the prime movers is supplied from a standard supply unit in which the sensing device is usually a gyroscope. The hydraulic power unit for the hydraulic fluid supply system is typically a variable volume pump and associated motor. A servo system is typically used to control the variable volume pump which supplies hydraulic pressure to the prime movers for orienting the fins. One of the several disadvantages of conventional hydraulic fluid supply systems is the lack of effective means to control the prime movers in a safe manner such that fin extension, retraction and tilting does not occur when the fin is not properly positioned for such movement.

A servo valve is a fluid valve that varies output flow or pressure in response to an input control signal system. Servo valves can be used to control the flow to and from hydraulic actuators and to control the volume output of a variable pump. The input electrical signal of the servo valve is converted into mechanical motion to actuate the servo valve control, usually by an electromagnetic torque motor. The servo valve can be pilotoperated in which case the mechanical movement of the torque motor is transmitted by the pilot into hydraulic power which controls the hydraulic output of the servo valve. Servo valves typically have electrical or mechanical feedback systems which compare the output with the input reference signal and make corrections to reduce the difference.

It is the main object of the present invention to provide a stabilizing fin for damping the rolling motion of a ship and which extends and stows athwartship.

A further object of the present invention is to provide a stabilizing fin which is extended and retracted in a simpler manner than those retractable fin systems known to the prior art.

A more specific object of the present invention is to provide a stabilizing fin in which the retraction and extension of the fin is accomplished without the introduction of hydraulic fluid into the fin support axle.

Still another object of the present invention is to ensure proper lubrication of the bearings used in the stabilizing fin chamber in a manner far simpler than that known to the prior art.

A further object of the present invention is to provide a stabilizing fin in which the drive shafts for the stabilizing fin and the prime movers can be properly and easily aligned.

A still further object of the present invention is to provide a stabilizing fin in which the guiderails for mounting the fin are properly leveled and aligned in a simpler and less costly manner than in those retractable fin systems known to the prior art.

Yet another object of the present invention is to provide an improved hydraulic fluid supply system for controlling the movement of the hydraulic actuators which position and orient the stabilizing fin.

Still another object of the present invention is to provide a pilot-operated servo valve usable with the improved hydraulic fluid supply system of the present invention and in other conventional applications.

Further objects and advantages of the present invention will become apparent upon reading the undergoing description when taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION The present invention broadly relates to a stabilizing fin for damping the rolling motion of a ship and which extends and stows athwartship. The stabilizing fin is rotatably mounted on a fin support axle and is adapted to be located athwartship in the operative position on one side of the ships hull below the water line. The fin support shaft is slideably mounted in a fin chamber located athwartship in a ships hull. A fin retraction shaft extends athwartship in the fin chamber and is rotatably mounted in the fin chamber. Outside the fin chamber and located in the ships hull are rotation means rotatably engaging the fin retraction shaft. The fin support axle has a central opening extending therethrough. Nut means are mounted in the central opening of the fin support axle. The outboard end of the fin retraction shaft extends into the central opening in the fin support axle and operatively engages the nut means. A fin tilting shaft extends athwartship in the fin chamber and is rotatably mounted in the fin chamber. Located outside the fin chamber and in the ships hull are rotation means rotatably engaging the fin tilting shaft. A cam having a pin attached to one of its faces is mounted on the fin support axle and rotatably engages the fin tilting shaft. A bifurcated fin tilting arm is attached to the stabilizing fin and the slot formed by its two branching members slidingly engages the pin attached to the cam.

Fin extension and retraction are accomplished as follows. The fin retraction shaft is rotated by the rotation means, typically a hydraulic motor and reduction gear, which engages the shaft. The fin retraction shaft is secured against movement in the athwartship direction. Accordingly, rotation of the fin retraction shaft causes the fin support axle and the stabilizing fin to extend or retract, depending upon the direction of rotation of the fin retraction shaft.

Tilting of the stabilizing fin occurs as follows. Activation of the rotation means rotatably engaging the fin tilting shaft causes rotation of the shaft. The fin tilting shaft in turn rotates the cam mounted on the fin support shaft. Rotation of the cam causes the pin carried by the cam to move along an arcuate path. The arcuate movement of the pin causes the pin to slide in the slot formed by the two branching members of the bifurcated fin tilting arm which in turn rotates and tilts the stabilizing fin.

The rotation means are hydraulic actuators which are controlled by a hydraulic fluid supply system. The hydraulic fluid supply system includes means, such as a variable volume pump and electric motor, for supplying hydraulic fluid under pressure to the hydraulic actuators for extending, retracting and tilting the stabilizing fin. A solenoid-operated valve controls the supply of hydraulic fluid to the hydraulic actuator for extending and retracting the stabilizing fin. The supply of hydraulic fluid to the solenoid-operated valve is in turn controlled by a pilot-operated valve which supplies hydraulic fluid to the solenoid-operated valve only when the stabilizing fin is properly positioned for fin extension and retraction. A servo valve controls the supply of hydraulic fluid to the hydraulic actuator for tilting the stabilizing fin. The supply of hydraulic fluid to the servo valve is in turn controlled by a pilot-operated valve which supplies hydraulic fluid to the servo valve only when the stabilizing fin is in the fully extended position.

The servo valve for controlling the supply of hydraulic fluid to the hydraulic actuator for tilting the stabilizing fin can be the novel hydraulic servo valve of the present invention. The servo valve includes a main spool housing. having a main spool chamber. The main spool housing contains supply and withdrawal ports for supplying and withdrawing working fluid to and from the main spool chamber from a working fluid reservoir. Transfer ports in the main spool housing function to transfer working fluid between the main spool chamber and the hydraulic actuator. A main spool is positioned in the main spool chamber and closes the transfer ports for transferring working fluid between the main spool chamber and the hydraulic actuator when the main spool is in the null position.

A pilot housing having a pilot sleeve chamber is associated with the main spool housing of the servo valve. The pilot housing contains supply and withdrawal ports for supplying and withdrawing pilot fluid to and from the pilot sleeve chamber from a pilot fluid reservoir. Transfer ports in the pilot housing function to transfer pilot fluid between the pilot sleeve chamber and the main spool housing. A pilot sleeve is positioned in the pilot sleeve chamber and defines a pilot spool chamber. Transfer ports in the pilot sleeve function to transfer pilot fluid between the supply, withdrawal and transfer ports in the pilot housing and the pilot spool chamber. A pilot spool is positioned in the pilot spool chamber and closes the transfer ports in the pilot sleeve which function to transfer pilot fluid between the transfer ports in the pilot housing and the pilot spool chamber when the pilot spool is in the null position.

Movement of the pilot spool in response to an input control signal at least partially opens the transfer ports for transferring pilot fluid between the transfer ports in the pilot housing and the pilot spool chamber. Transfer ports in the main spool housing function to transfer pilot fluid from the pilot housing to the main spool chamber to move the main spool and at least partially open the transfer ports for transferring working fluid between the main spool chamber and the hydraulic actuator. Means are provided, such as a bell crank and mechanical feedback linkage, which are responsive to the hydraulic actuator for moving the pilot sleeve and closing the transfer ports for transferring fluid between the pilot housing and the pilot spool chamber to thereby deactivate the hydraulic actuator by stopping the transfer of working fluid between the main spool chamber and the hydraulic actuator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view, partly in section, of the retractable stabilizing fm of the present invention, the retracted position being shown in phantom lines;

FIG. 2 is an enlarged transverse sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is an enlarged transverse sectional view, taken on the line 3-3 of FIG. 1, but showing the stabilizing fin in a tilted position;

FIG. 4 is an enlarged fragmentary plan view, partly in section, of the retraction and tilting drive means for the stabilization fin;

FIG. 5 is an enlarged fragmentary horizontal sectional view illustrating the fin retraction and fin tilting mechanism for the stabilization fin;

FIG. 6 is an enlarged fragmentary horizontal sectional view of the outboard end of the stabilizing fin;

FIG. 7 is a transverse view, partly in section, of the stabilizing fin guiderail leveling method of the present invention;

FIG. 8 is an enlarged transverse view, partly in section, taken on the line 8-8 of FIG. 1 and showing the fin retraction shaft position indicator of the present invention;

FIG. 9 is a schematic representation of the electric circuitry for energizing the solenoids which control the extension and retraction of the stabilizing fin of the present invention;

FIG. 10 is a schematic representation of the electric circuitry which controls the tilting of the stabilizing fin of the present invention;

FIG. 11 is a schematic representation of the hydraulic circuitry which controls the extension, retraction and tilting of the stabilizing fin of the present invention; and

FIG. 12 is an enlarged vertical sectional view of the novel servo valve of the present invention operating a typical hydraulic actuator shown partly in section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 through 6, fin chamber 10 is located athwartship in a ship s hull (not shown). The fin chamber is of appropriate size to accommodate the stabilizing fin in its retracted or inoperative position. The fin chamber 10 includes a fin chamber shell 12, a stern plate 14 and a fin chamber collar 16. The fin chamber collar is welded or otherwise fixedly attached to the hull of the ship. Stiffeners 18 function to give rigidity and structural support to the fin chamber and additionally function as water tight seals at their connection between the fin chamber shell 12 and the fin chamber collar l6.

Fin support axle 20 extends athwartship in the fin chamber and is slidably mounted on lower and upper guiderails 22 and 24, respectively, by means of inboard sliding shoe mount 26 and outboard sliding shoe mount 28. Each of the guiderails are fixed to flanges which form part of box girders 29. Stabilizing fin 30 is rotatably mounted on fin support axle 20 by means of outboard andinboard radial bearings 32 and 34, respectively, and is adapted to be located athwartship in the operative position on one side of the ships hull below the water line. Tail flap 36 is pivotally attached to the stabilizing fin by hinge 38. The tail flap and stabilizing fin will lie in the same generally horizontal plane when the stabilizing fin is fully retracted in its inoperative position, and also when the stabilizing fin has been fully extended into its operative position, but before it has been rotated on the fin support axle.

Fin retraction shaft 40 extends athwartship in fin chamber 10 and is rotatably mounted to the fin chamber by means of radial bearings 42. The outboard end of the fin retraction shaft 40 has an external screw thread as shown in the figures. The fin retraction shaft is mounted so that it is non-movable in the athwartship direction. Rotatably engaging fin retraction shaft 40 and located outside fin chamber 10 and in the ships hull are means for rotating the fin retraction shaft, including a hydraulic motor 44 and reduction gear 46.

Fin support axle 20 has a central, longitudinal opening 48 which is cylindrical in shape and functions as the fin retraction shaft receiving chamber. Mounted in central opening 48 of fin support axle 20 at the-inboard end thereof is nut means 50 which has an internal screw thread. The outboard end of fin retraction shaft 40 extends into central opening 48 in fin support axle 20 and operatively engages nut means 50 by being threaded therein. A retaining device 52 is mounted on the outboard end of fin retraction shaft 40 and in central opening 48. This retaining device slidably and rotatably engages the walls of the central opening in the fin support axle so that the fin retraction shaft can be easily moved longitudinally in the central opening in the fin support axle.

Fin tilting shaft 54 extends athwartship in fin chamber 10 and is rotatably mounted to the fin chamber by means of radial bearings 56. The fin tilting shaft is mounted so that it is non-movable in the athwartship direction. Rotatably engaging fin tilting shaft 54 and located outside fin chamber 10 and in the ships hull are means for rotating the fin tilting shaft, including a reciprocating torque actuator 58.

A cam 60 having a pin 62 fixedly attached to its outboard face is rotatably mounted. in the outboard sliding shoe mount 28. Cam 60 has a central, longitudinal opening 64 which is cylindrical in shape and functions as a receiving chamber for the fin tilting shaft 54. The outboard end of fin tilting shaft 54 extends into central opening 64 of cam 60. Cam 60 rotatably engages fin tilting shaft 54 by means of square bearing 66 such that a rotation of fin tilting shaft 54 causes an equal rotation of cam 60.

Bifurcated fin tilting arm 68 is fixedly attached to stabilizing fin 30. The slot 70 formed by its two branching members 72 and 74 slidingly engages pin 62 attached to cam 60 such that stabilizing fin 30 rotates on fin support axle 20 when the cam is rotated. Bifurcated tail flap tilting arm 76 is fixedly attached to tail flap 36. The slot 78 formed by its two branching members 80 and82 slidingly engages pin 83. Pin 83 is fixedly attached to outboard sliding shoe mount 28.

Referring now in detail to FIG. 4, rear mounting plate 84 is welded to stem plate 14 of fin chamber 10. Rear mounting plate 84 has two openings therein through which fin retraction shaft 40 and fin tilting shaft 54 pass. Fin retraction shaft 40 and fin tilting shaft 54 are rotatably mounted to fin chamber 10 in exactly the same manner. Accordingly, like reference numerals will be used to identify like parts with the exception of radial bearings 42 and 56 and only the mounting of fin retraction shaft 40 will be discussed in detail.

Mounting housing 86 is generally rectangular in shape and extends into a rectangular opening in rear mounting plate 84. Mounting housing 86 has a rectangular flange whose outboard face is in abutting relationship with the inboard face of rear mounting plate 84. Bolts 87 extend through the rectangular flange of mounting housing 86 and into rear mounting plate 84 and detachably mount mounting housing 86 to rear mounting plate 84. Gland housing 88 is cylindrical in shape and extends into the cylindrical opening in mounting housing 86. Gland housing 86 has a radial flange whose outboard face is in abutting relationship with the inboard face of mounting housing 86. Bolts 89 extend through the radial flange of the gland housing 88 and into mounting housing 86 and detachably mount gland housing 88 to mounting housing 86.

Gland housing 88 for fin retraction shaft 40 houses radial bearing 42 which bears against fin retraction shaft 40 and allows the fin retraction shaft to be easily rotated. Gland housing 88 also houses seal 92, such as Chevron packing, for sealing off the inside of a ships hull from the water which fills the inside of fin chamber 10. The inboard end of radial bearing 42 and the outboard end of seal 92 abut against shoulder 90 of gland housing 88. Shoulder 90 of gland housing 88 separates radial bearing 42 from sea] 92. Seal 92 is of split configuration so that it can easily slide over the end of fin retraction shaft 40. Bearing ring 94 is housed in gland housing 88 and has its outboard end in abutting relationship with and acts to compress seal 92 against shoulder 90. A radial bearing nut 96 having internal screw thread is threaded onto gland housing 88 and into abutting relationship with the inboard end of bearing ring 94. Threading of nut 96 onto gland housing 88 expands the Chevron packing and increases the seal between gland housing 88 and fin retraction shaft 40. Nut 96 can be unthreaded from gland housing 88 and bearing ring 94, and seal 92 removed for replacement or repair. Annular retaining plate 98 is bolted by bolts 99 to the outboard end of gland housing 88 and into abutting relationship with the outboard end of radial bearing 42. Annular retaining plate 98 is slightly spaced from fin retraction shaft 40 so that water can enter the interior of gland housing 88 and lubricate radial bearing 42.

Bolted (not shown) to the mounting housing 86 and surrounding fin retraction shaft 40 is coupling housing 100. Coupling housing 100 is preferably a unitary metal casting and serves to mount hydraulic motor 44 and reduction gear 46 to fin chamber and to house the thrust bearings, hydraulic motor coupling and sprocket gear 102.

Coupling housing 100 has radially and inwardly extending shoulder 104 which bears against outboard thrust bearings 106. Outboard thrust bearings 106 are retained in place by retaining plate 108 which is bolted to the coupling housing. Access to outboard thrust bearings 106 and to radial bearing nut 94 is provided by access ports 110 in the coupling housing. Coupling housing 100 also carries a radially and inwardly extending shoulder 112 which bears against inboard thrust bearings 114. Inboard thrust bearings 114 are retained in place by retaining plate 116 which is bolted to coupling housing 100.

Metal retaining nut 119 is threaded onto the inboard end of fin retraction shaft 40 and is used to adjust the tightness'of shaft 40 in relation to thrust bearings 114. Inboard and outboard closure rings 117 and 115, re spectively. are press fitted and spring-held'in position and provide a fluid and dust tight enclosure for thrust bearings 114 and 106, respectively.

The thrust bearings not only allow for easy rotation of fin retraction shaft 40, but also transmit longitudinal forces acting on the fin retraction shaft to coupling housing 100. Outboard thrust bearings 106 function to transmit inwardly directed forces exerted on fin retraction shaft 40 upon extension of stabilizing fin 30 to coupling housing 100. In like manner, inboardthrust bearings 114 function to transmit outwardly directed forces exerted on the fin retraction shaft 40 upon'retraction of stabilizing fin 30 to coupling housing 100.

Inwardly directed forces exerted on fin retraction shaft 40 are transmitted to thrust bearings 1 06 through shoulder 109 on fin retraction shaft 40 which is in abutting contact with the thrust race of thrust bearings 106. In like manner, outwardly directed forces are transmitted to bearings 114 through nut 119 which is in threaded engagement with fin retraction shaft 40. The a outboard face of nut 119 is in abuttment with the thrust race of bearings 114 and transmits longitudinal force therethrough.

Fin retraction shaft 40 is coupled to its rotation means by a standard coupling 118 contained in coupling housing 100. Coupling housing has access ports 122 which provide access to inboard thrust bearings 114 and to coupling 118. Reduction gear 46 and hydraulic motor 44 are attached to coupling housing 100 by bolts 124. The reduction gear and hydraulic motor are standard equipment and do'not require specific description.

Bolted (not shown) to mounting housing 86'and surrounding fin tilting shaft 54 is coupling housing 126. Coupling housing 126 is preferably a unitary metal casting similar to coupling housing 100 and serves to mount reciprocating torque actuator 58 to fin chamber 10 and to house the thrust bearings and reciprocating torque actuator coupling. Coupling housing 126 has radially and inwardly extending shoulder 128 which bears against the outboard end of thrust bearing 132. Annular retaining plate 130 is bolted to coupling housing 126. The outboard face of annular retaining plate 130' abuts against the inboard face of thrust bearings 132 and serves to retain the thrust bearings in their housing provided by coupling housing 126. Metal retaining nut 134 is threaded onto the inboard end of fin tilting shaft 54 and is used to adjust the tightness of thrust bearings 132. Inboard and outboard closure rings 137 and 136, respectively, are press fitted and spring-held in position and provide a fluid and dust tight enclosure for thrust bearings 132 so that the thrust bearings can be properly lubricated. Thrust bearings 132 not only allow for easy rotation of fin tilting shaft 54 but also transmit longitudinal forces acting on the fin tilting shaft to couplings;

housing 126. However, these longitudinal forces are not as great as with respect to fin retraction shaft 40.

Fin tilting shaft 54 is coupled to its rotation means by e i a standard coupling 138 contained in coupling housing 126. For example, the coupling can comprise an involute spline on the inboard end of fin tilting shaft 54 which is fitted into a corresponding involute spline on I the outboard end of the drive shaft of the reciprocating torque actuator 58. Coupling housing 126 contains access port 139 which allows access to radial bearing nut I 96 threaded to gland housing 88 and further access port 140 which allows access to coupling 138. Bolted to coupling housing 126 by retaining bolts 142 is reciprocating torque actuator 58. The reciprocating torque actuator is of conventional type and can be controlled to rotate the fin tilting shaft in either a clockwise or counterclockwise direction by proper introduction of hydraulic fluid.

Referring again to FIG. 4, the previously described means of mounting fin retraction shaft 40 and hydraulic motor 44 and reduction gear 46 to fin chamber allows fin retraction shaft 40 to be easily and properly aligned with the drive shaft from hydraulic'motor 44 and reduction gear 46. In like manner, the previously described means of mounting fin tilting shaft 54 and reciprocating torque actuator 58 to fin chamber 10 allows fin tilting shaft 54 to be easily and properly aligned with the drive shaft from reciprocating torque actuator 58. Referring in particular now to the alignment of fin retraction shaft 40 and the drive shaft of hydraulic motor 44 and reduction gear 46, rear mounting housing 86 is bolted to rear mounting plate 84, which is welded to stem plate 14 of fin chamber 10, such that fin retraction shaft 40 will pass through the center of the fin retraction shaft opening in rear mounting housing 86 when fin retraction shaft 40 is properly mounting on guiderails 22 and 24. The diameter of gland housing 88 is sufficiently smaller than the diameter of the fin retraction shaft opening in rear mounting housing 86 such that gland housing 88 can be easily centered around fin retraction shaft 40 before being bolted to rear mounting housing 86. Gland housing 88 will be in concentric alignment with the drive shaft of hydraulic motor 44 and reduction gear 46 by virtue of closely machined openings at each end of coupling housing 100 into which gland housing 88 and reduction gear 46, respectively, fit. The drive shaft of hydraulic motor 44 and reduction gear 46 will be properly aligned with fin retraction shaft 40 once the hydraulic motor and reduction gear are bolted in place. In similar manner, fin tilting shaft 54 is properly aligned with the drive shaft of reciprocating torque actuator 58.

Male locking member 144 is welded to stem plate 14 of fin chamber 10 and is adapted to mate with female locking member 146 carried by inboard sliding shoe mount 26. A cover plate 148 is removably attached to fin chamber 10. When stabilizing fin 30 is in its fully retracted position and male locking member 144 is in mating relationship with female locking member 146, cover plate 148 can be removed and a retaining device such as a horseshoe washer placed over the outboard end of the male locking member, thus locking the stabilizing fin against extension.

Referring now particularly to FIG. 5, the outboard end of fin retraction shaft 40 extends into central opening 48 of the fin support axle and is threaded into nut means 50. The inboard end of the nut means carries a radial flange 150 which mates with the inboard end of fin support axle 20. Nut means 50 is bolted to the fin support axle by means of retaining plate 153 and a plurality of bolts 152. Flange 150 not only serves as a means of securing nut means 50 to fin support axle 20, but as a means of transmitting longitudinal forces caused by rotation of fin retraction shaft 40 during extension and retraction to the fin support axle. Retaining plate 154 on the outboard end of nut means 50 acts as a stop for fin retraction shaft 40 when stabilizing fin 30 is fully extended.

Fin retraction shaft 40 carries retaining device 52 on its outboard end. A basic function of this device is to prevent the fin retraction shaft from flexing, particularly when the stabilizing fin is fully retracted and the retaining device occupies a position at the outboard end of the central opening in the fin support shaft. Retaining device 52' includes a shaft 156 which is not threaded but which carries threaded shaft 158 on its outboard end for receiving retaining nut 160. Mounted on retaining device shaft 156 are inboard and outboard radial bearings 162 and 164, respectively, which are cylindrical in shape and have radial flanges such that they are L-shaped in cross section and which are combined to form a U-shaped bearing. Metal roller 166 is cylindrical in shape and surrounds the base of the U-shaped bearing which holds metal roller 166 in place on retaining device shaft'156. End plates 168 and 170 attached on the inboard and outboard ends of retaining device 52, respectively, serve to retain the U-shaped radial bearing in position. Metal roller 166 can rotate freely on the U-shaped radial bearing. By virtue of this arrangement, retaining device 52 can easily rotate in the central opening 48 of the fin support shaft 20 and can slide back and forth therein. This easy movement is further enhanced by a water-lubricated bearing lining 172 which is on the inner surface of central opening 48 in the fin support axle 20. The bearing lining provides a good water-lubricated sliding surface when in contact with metal roller 166.

Radial bearings 162 and 164 and nut means 50 are of the type which are lubricated by water. Water is continually present in fin support axle 20 when the ship is at sea since central opening 48 of fin support axle 20 extends completely therethrough. Accordingly, water leaks by radial bearing 162 and 164 and metal roller 166 in retaining device 52, lubricates radial bearings 162 and 164, and then passes between fin retraction shaft 40 and nut means 50, thereby lubricating the nut means.

Any of various conventional materials can be used for water-lubricated radial bearings 162 and 164 and nut means 50 as well as for the other water-lubricated bearings used in the fin chamber. Illustrative of bearing materials which are lubricated by water are the line of heavy duty, thermosetting, plastic materials made from fabric impregnated with phenol-formaldehyde resins which is compressed under heat into a permanently solid substance with high structural properties and sold under the tradename Micarta.

Referring now in more detail to the cam actuated fin tilting arm and having particular reference to FIGS. 2, 3, and 5, cam 60 is rotatably mounted in outboard sliding shoe mount 28, which is in turn fixedly mounted to fin support axle 20. Cam 60 includes cylindrical sleeve 174 which carries cam arm 176 on its outboard end. Cam arm 176 lies at a right angle to the longitudinal axis of cylindrical sleeve 174 and is oval in shape as more particularly seen in FIGS. 2 and 3. Cam arm 176 carries round pin 62 on its outboard face. Pin 62 is fixedly attached to cam arm 176 so that there is no relative rotation between the two. Cam 176 is mounted in outboard sliding shoe mount 28 so that the longitudinal axis of cylindrical sleeve 174 is parallel to the major axis of fin support axle 20.

Outboard sliding shoe mount 28 has a cylindrical opening 178 into which cylindrical sleeve 174 of cam 60 is mounted. Cam 60 is rotatably mounted to outboard slidingshoe mount 28 by means of inboard and outboard bearings 180 and 182, respectively, which are L-shaped in cross section. Outboard bearing 182 allows easy rotation of cylindrical sleeve 174 and cam arm 176 relative to outboard sliding shoe mount 28. Although the inboard end of outboard sliding shoe mount 28 which receives cylindrical sleeve 174 is shown as being a separate part, this part can be integral with the remainder of outboard sliding shoe mount 28. Inboard bearings 180 are held in place by cam end plate 184 which has a bearing surface which allows easy rotation of cam 60.

Fin tilting shaft 54 is square in shape and extends into central opening 64 of cam 60. Surrounding fin tilting shaft 54 is square bearing 66 which functions to trans mit the rotational movement of the fin tilting shaft to cylindrical sleeve 174 of cam 60. Although square bearing 66 is capable of transmitting rotational movement, it also functions to allow fin tilting shaft 54 to easily slide through cylindrical sleeve 174 when stabilizing fin 30 is being retracted or extended. Square bearing 66 is held in place by having its outboard end in abutting relationship with a portion of cylindrical sleeve 174 and by having its inboard end retained against inward movement by cam end plate 184. Central opening 64 in the sleeve of the cam allows water to lubricate square cam bearing 66. Likewise, the other bearings used to mount cam- 60 to outboard sliding shoe mount 28 are also open to the water and are lubricated thereby.

Fixedly attached to stabilizing fin 30 is bifurcated fin tilting arm 68. The two branching members 72 and 74 of bifurcated fin tilting arm 68 form rectangular slot 70 which engages pin 62 attached to the outboard face of cam arm 176. Pin 62 carries a square bearing block 186 which slides back and forth in slot 70 when cam arrn 176 is rotated. Receiving chamber 188 is provided in stabilizing fin 30 and receives the outboard end of fin tilting shaft 54 when the stabilizing fin is retracted.

The center of rotation of cam 60 is the longitudinal center line of fin tilting shaft 54 and the center of rotation of stabilizing fin 30 is the longitudinal center line of fin support axle 20. The radius of rotation of cam 60 is the distance between the center line of cam pin 62 and the cams center of rotation. In like manner, the radius of rotation of stabilizing fin 30 is the distance between the point of attachment of bifuricated fin tilting arm 68 to stabilizing fin 30 and the stabilizing fins center of rotation. Since the radius of rotation of stabilizing fin 30 is greater than the radius of rotation of the cam 60, the angle at which stabilizing fin 30 is tilted will be proportionally less than the angle at which the cam 60 is rotated. For example, if the radius of rotation of stabilizing fin 30 is three times larger than the radius of rotation of cam 60, stabilizing fin 30 will tilt at an angle which is approximately one-third of the angle at which cam 60 is rotated. Since cam 60 rotates through the same angle through which fin tilting shaft 54 rotates, it will be seen that when the radius of rotation of stabilizing fin 30 is approximately three times larger than the radius of rotation of cam 60, a 90 rotation of fin tilting shaft 54 will only result in approximately a 30 tilting of stabilizing fin 30.

Inboard journal bearing 190 is mounted to fin support axle 20. Journal bearing 190 may be, for example, an annular stainless steel ring which is shrunk fitted to the exterior of fin support axle 20. The inboard end of stabilizing fin 30 is rotatably mounted on journal bearing 190 by means of inboard radial bearing 34. There is 1 2 no longitudinal movement of stabilizing fin 30 relative to fin support axle 20, and stabilizing fin 30 and fin support axle 20 extend and retract in unison.

Tail flap 36 is pivotally hinged by tail flap hinge 38 to stabilizing fin 30.'Attached to tail flap 36 is tail flap tiltin g arm 76. Tail flap tilting arm 76 is bifurcated and has a rectangular slot 78 formed by its two branching members 80 and 82. Outboard sliding shoe mount 28 carries pin 83 which is fixedly attached thereto by means of nut 192 threaded to the inboard end of pin 83. The longitudinal axis of pin 83 is parallel to the longitudinal axis of fin support axle 20. Pin 83 has a round head 194 which carries a square bearing block 196. Slot 78 of bifurcated tail flap tilting arm 76 engages square bearing block 196 so that square block 196 can slide back and forth in slot 78. Square bearing blocks 186 and 196 are both open to and lubricated by the water which fills the interior of fin chamber 10.

The center of rotation of the tail flap 36 is the longitudinal center line of fixed pin 83. The radius of rotation of tail flap 36 is the distance between the longitudinal center line of fixed pin 83 and hinge 38. The center of rotation of the trailing edge of stabilizing fin 30 (i.e., the point at which tail flap 36 is hinged to stabilizing fin 30) is the longitudinal center line of fin support axle 20. The radius of rotation of the trailing edge of stabilizing fin 30 is the distance between the longitudinal center line of fin support axle 20 and the longitudinal center line of hinge 38. Since the radius of rotation of tail flap 36 is less than the radius of rotation of the trailing edge of stabilizing fin 30, tail flap 36 will be tilted to a proportionally larger angle than the angle to which stabilizing fin 30 is tilted. For example, if the radius of rotation of tail flap 36 is one-half the radius of rotation of the trailing edge of stabilizing fin 30, tail flap 36 will be tilted at an angle which is approximately twice the angle at which stabilizing fin 30 is tilted. For example, using the illustration of the relationship between the tilting of the stabilizing fin relative to the rotation of the fin tilting shaft above, if fin tilting shaft 54 is rotated through an angle of cam arm 176 will in turn be rotated through and angle of 90, stabilizing fin 30 will be rotated through an angle of approximately 30 and tail flap 36 will be rotated through an angle of approximately 60. This relationship is clearly illustrated in FIG. 3.

Turning to the attachment of the stabilizing fin to the outboard end of the fin support axle and with particular reference to FIG. 6, outboard journal bearing 198 is mounted to the outboard end of fin support axle 20. Journal bearing 198 is typically made of stainless steel which is shrunk fitted to fin support axle 20. Journal bearing 198 is provided with an outwardly extending flange 200 on its inboard end. Inboard annular bearing 202 has its inboard face in abutting relationship with flange 200 on journal bearing 198 and has its outboard face in abutting relationship with structural support 204 of stabilizing fin 30. Journal bearing 198 carries outboard annular bearing 206 which has its inboard face in abutting relationship with structural support 204 of stabilizing fin 30 and has its outboard face in abutting relationship with fin support shaft end plate 208. Outboard radial bearing 32 rotatably mounts stabilizing fin 30 to fin support axle 20. Flange 200 carried by journal bearing 198 transmits longitudinal forces developed by the extension of fin support axle 20 to stabilizing fin 30. In like manner, fin support axle end plate 208 transmits longitudinal forces developed by the retraction of fin support axle to stabilizing fin 30. The inboard and outboard annular bearings 202 and 206 and radial bearing 32 allow'stabilizing fin to freely rotate on fin support axle 20. The diameter of the fin support axle end plate 208 is larger than the diameter of fin support axle 20. End plate 208 is fixed to the end of fin support axle 20 by bolts 215. By this arrangement, stabilizing fin 30 is not free to move'longitudinally relative to fin support axle 20but is free to rotate on fin support axle 20 when tilted by fin tilting shaft 54.

Removable cover plate 210 provides access to fin bearing access chamber 212 for repair and replacement of the fin bearings. Vent pipe 214 allows water to enter fin bearing access chamber 212 and pass into central opening 48 of fin support shaft 20 and between fin support axle 20 and stabilizing fin 30 to lubricate the bearings therein. Vent pipe=214 also provides end access for boring bars or other forming tools for machining or aligning longitudinal bores in the-fin bearings. e v

The method of the present invention for leveling and aligning the stabilizing fin guiderails is shown in- FIG. 7. This method can be used to. level upper and lower guiderails 22 and 24 in FIGS. 2 and 3. Box'girder 220 is a typical supportfor a stabilizing fin guiderail and is composed of lower flange 222, upper flange 224, and webs 226. Box girder 220 would typically be attached to a fin chamber by welding lowerflange 222 to fin chamber collar 228 and by welding upper flange 224 to fin chamber shell 230. It should be understoodyhowever, that the type of support for the stabilizing fin guiderail and the method of attaching the support to the fin chamber is not critical to the present leveling method. Guiderail 232 is placed on upper flange 224 of box girder 220 and properly aligned. Level adjusting means such as level adjusting screws 234 are then placed through guiderail 232 and into contact with the abutting surface of upper flange 224. In the figure, level adjusting screws 234 are illustrated as jack screws. Level adjusting screws 234 are placed at appropriate positions along the length of guiderail 232 and are used to adjust the level of guiderail 232 with respect to the abuttifig surface of upper flange 224.

After the level of guiderail 232 has been adjusted,the space between guiderail 232 and upper flange 224 is filled with a filler material 236 which can be poured into the space betweengu'iderail 232 and upper flange 224 and will become permanently rigid upon setting or upon being heated or cured. Filling material 236 is typically a plastic and particularly a thermosetting resin such as an epoxy resin which can be easily forced into the space between guiderail 232 and upper flange 234. After filling material 236 becomes rigid, means are attached to the guiderail and support, such as hold down bolts 238, to hold guiderail 232 in a fixed position relative to box girder 220. Retaining bars 240 are welded in position to act as forms or cofferdams to confinefilling material 236 while it is in a fluid state and to act asa securing means to prevent movementof filling material 236 relative to the surface of upper flange 224. Level adjusting screws 234 are then removed and the guide surface of guiderail 232 is in position to receive the fin sliding shoe mounts. The stabilizing fin is then slidably 14 Referring now in particular to FIGS. 1 and 8, indicator housing 250 is bolted to coupling housing 100. Reduction gear 252 is housed to indicator housing 250.

.Reduction gear 252 is attached to sprocket gear 102 mounted on guiderail 232. By using the leveling method of the present invention,,it is not necessary to machine the abutting surfaces o fupper flange 234 and guiderail 232 and, additionally, the time consuming addition and removal of metal shims is avoided.

mounted on fin retraction shaft 40 and housed in coupling housing by drive chain 254.

Attached to indicator housing 250 are electrical limit switches 256 and 258 and hydraulic pilot valve 362. Actuator arm 260 is attached to the output drive shaft of reduction gear 252. When stabilizing fin 30 is in the fully retracted position actuator arm 260 closes limit switch 256 by camming action. Reduction gear 252 is sized with a knowledge of the number of threads per lineal inch on fin retraction shaft 40 and the overall length of fin chamber 10 such that actuator arm 260 rotates on extension of stabilizing fin 30 and closes limit switch 258 when stabilizing fin 30 is in the fully extended position. Actuator arm 260 also actuates pilot valve 362 by camming action when stabilizing fin 30 is in the fully extended position and places pilot valve 362 in the cam offset position. The closing of limit switch 256 conditions the electric circuitry which operates the extension of stabilizing fin 30 so that stabilizing fin 30 can be extended on command. In like manner, the closing of limit switch 258 conditions the electric circuitry which operates the tilting of stabilizing fin 30 so that stabilizing fin 30 can be tilted on command and also conditions the electric circuitry which operates the retraction of stabilizing fin 30 so that stabilizing fin 30 can be retracted on. command. The, placing of .pilot valve 362 in the'cam-offset position conditions. the hydraulic circuitry which supplies hydraulic fluid to reciprocating torque actuator 58 so that the stabilizing fin 30 can be tilted on command. v

Pilot valve 342 is mountedion coupling housing 126 as shown in FIG. 1. Pilot valve342 has vertical arm 343 which is contactedand moved by,-,cam 343 shown in FIG. 4. Cam 343 is mounted on fin tilting shaft 54 and is positioned such that vertical arm 343 isonly moved when stabilizing fin 30 is in the non-tilted and substantially horizontal position and therefore ready to be-extended or retracted. Movement of arm 343 puts pilot valve 342 in the cam offset position and conditions the hydraulic circuitry which supplies hydraulic fluid to hydraulic motor 44 sozthat the stabilizing fin 30 can be extended or retracted on command. I

Referring now to FIG. 9, a schematic representation is shown of the electric circuitry. for energizing solenoids 351 and 353 which control the extension and retraction of stabilizing fin 30. Power source 270 supplies power for energizing fin extension solenoid 351 and fin retraction solenoid 353. Bridge control switch 272 controls the energizing of fin extension solenoid 351 and in like manner bridge'c'ontrol switch 274 controls the energizing of fin retraction solenoid 353. Fin extension solenoid 351 cannot be energized until its circuit is conditioned by closing limit switch 256. In like manner, fin retraction solenoid 353 cannot be energized until limit switch 258 is closed. As previously described, limit switches 256 and 258 are mechanically closed by actuator arm 260 which is attached to the drive shaft of reduction motor 252. Limit switch 256 is closed by actuator arm 260 when stabilizing fin 30 is in the fully retracted position. In like manner, limit switch 258 is closedby actuator arm 260 when stabilizing fin 30 is in the fully extended position.

The operation of the energizing circuitry for solenoids 351 and 353 will now be described starting with the stabilizing fin 30 in the fully retracted position. In this position, actuator arm 260 mechanically closes by camming action limit switch 256. When switch 256 is closed, relay 256 is energized causing contact 256" to close and contact 256" to open. The fin extension solenoid 351 circuit is now conditioned and ready to be energized to extend stabilizing fin 30 on control from the bridge. When the rolling motion of a ship has reached an unacceptable level, the captain closes bridge control switch 272 thereby energizing fin extension solenoid 351 through relay contact 272", and causing stabilizing fin 30 to extend from the side of the ships hull. At the same time, actuator arm 260 driven by the drive shaft of reduction gear 251 moves away from limit switch 256 and toward limit switch 258. When stabilizing fin 30 is in the fully extended position, actuator arm 260 mechanically closes limit switch 258. Closing of switch 258 causes relay 258' to open contact 258" de-energizing relay 272' and closing contact 258" to condition the fin retraction circuit. Accordingly, fin extension solenoid 351 is de-energized and fin retraction shaft 40 will cease rotating. The fin retraction solenoid 353 circuit is now conditioned and ready to be energized to retract stabilizing fin 30 on command from the bridge.

After the captain determines that use of stabilizing fin 30 is no longer required, bridge control switch 274 is closed and fin retraction solenoid 353 energized through relay contact 274". Energizing of fin retraction solenoid 353 causes stabilizing fin 30 to retract and at the same time causes actuator arm 260 to move away from limit switch 258 and toward limit switch 256. When stabilizing fin 30 is in the fully retracted position, actuator arm 260 mechanically closes limit switch 256 by camming action and energizes relay 256. Relay 256' opens contact 256" de-energizing relay 274 thereby stopping the rotation of fin retraction shaft 40 and closes contact 256" conditioning the fin extension circuit. Stabilizing fin 30 is now in the fully retracted position and the fin extension solenoid 351 circuit conditioned for energizing solenoid 351 on proper command from the bridge.

A schematic representation is shown in FIG. 10 of the electric circuitry which controls the tilting of stabilizing fin 30 and the manner in which the circuitry is conditioned so that stabilizing fin 30 can be tilted. The

standard control unit for stabilizing fins usually employs a gyroscope sensing device. The gyroscope senses roll angle and rate of roll, and sometimes roll acceleration as well. The data received by the gyroscope is evaluated by a computer and a gyro command 280 is amplified in amplifier 282 and transmitted to the prime movers which orient the fins so that the fins compensate for the disturbing moment of the waves. In the present instance, the amplified signal is sent to a servo valve 372 which supplies hydraulic fluid to reciprocating torque actuator 58. Feedback potentiometer 378 is employed when an electrical feedback system is desired to stop the tilting of stabilizing fin 30 at the position commanded'by gyro command 280. According to the present invention, means are provided for electrically preventing the actuation of reciprocating torque actuator 58 until stabilizing fin 30 is in the fully extended position and ready to be tilted. Contact 258" in limit switch 258 is spring-biased so that it will remain open unless closed by relay 258' as shown in FIG. 9. When contact 258' is opened, no gyro command signal 280 can be fed to servo valve 372, and accordingly, reciprocating torque actuator 58 cannot be actuated. Limit switch 258 is mechanically closed by actuator arm 260, relay 258' energized and contact 258" closed when stabilizing fin 30 is in the fully extended position. When stabilizing fin 30 leaves the fully extended position, actuator arm 260 moves away from limit switch 258, relay 258 is de-energized and contact 258"" is opened. Accordingly, reciprocating torque actuator 58 can only be operated'when stabilizing fin 30 is in the fully extended position.

Having described the structural elements of the present stabilzing fin and the conditioning of the electric and hydraulic circuits for controlling the hydraulic actuators which operate the fin, a general description will now be given of the interaction of these elements to affect extension, retraction and tilting of the stabilizing fin. Fin extension and retraction are accomplished as follows. Actuation of the hydraulic motor 44 and reduction gear 46 causes rotary motion to be transmitted to fin retraction shaft 40 by coupling 118. Fin retraction shaft 40 freely rotates on thrust bearings 106 and 114 and on radial bearing 42 in gland housing 86. The threaded outboard end of fin retraction shaft 40 rotates in nut means 50 which is mounted in central opening 48 in fin support axle 20. Fin retraction shaft 40 is fixed against movement along its longitudinal axis, however, fin support axle 20 is free to move in and out of fin chamber 10 since it is attached to inboard and outboard sliding shoe mounts 26 and 28, respectively, which are free to slide on lower and upper guiderails 22 and 24, respectively. Accordingly, rotation of fin retraction shaft 40 causes fin support axle 20 and the stabilizing fin 30 to retract or extend depending upon the direction of rotation of the fin retraction shaft.

When fin retraction shaft 40 rotates, its retaining device 52 also rotates and slides in or out in central opening 48 of fin support axle 20. Retaining device 52 prevents flexing of fin retraction shaft 40, particulary when fin support axle 20 and stabilizing fin 30 are moved into the fully retracted position. As stabilizing fin 30 is retracted, fin tilting shaft 54 passes through central opening 64 in cylindrical sleeve 174 of cam 60 and then into fin tilting shaft receiving chamber 188 of stabilizing fin 30. If stabilizing fin 30 is fully retracted, male locking member 144 mates with female locking member 146 such that stabilizing fin 30 can be secured against extension.

Tilting of stabilizing fin 30 occurs as follows. When stabilizing fin 30 is in its fully extended and operative position, hydraulic fluid is introduced into reciprocating torque actuator 58 and results in a torque being applied to fin tilting shaft 54 by means of coupling 128. Fin tilting shaft 54 freely rotates in fin chamber 10 on radial bearing 56 contained in gland housing 86. The rotary motion of fin tilting shaft 54 is transmitted to cam 60 by square bearing block 66 surrounding fin tilting shaft 54 in cylindrical sleeve 174 of cam 60. Cam 60 rotates in outboard sliding shoe mount 28 and cam arm 176 and cam pin 62 carried on its outboard face experience the same angular rotation as fin tilting shaft 54. Cam pin 62 slides in slot 70 formed by the branching members 72 and 74 of bifurcated fin tilting arm 68. The arcuate movement of the cam arm 176 and cam pin 62 cause stabilizing fin 30 to rotate on inboard and outboard journal bearings and 198 attached to fin support axle 20. The fin support axle does not rotate and remains stationary during fin tilting. Tilting of stabilizing fin 30 causes tilting of tail flap 36 which is attached to stabilizing fin 30 by hinge 38. Tail flap 36 ro- 17 tates about fixed pin 83 and because of this rotation, pin 82 slides back and forth in slot 78 formed by the branching members 80 and 82 of bifurcated tail flap tilting arm 76.

Fin extension, retraction and tilting are performed by means of standard hydraulic actuators. The hydraulic circuitry for supplying hydraulic fluid to the hydraulic actuators for the starboard fin is shown in FIG. 1 1. The hydraulic circuitry for supplying hydraulic fluid to the port side fin is identical to the circuitry shown in FIG. 11. Hydraulic fluid is stored in reservoir 300. Reservoir 300 has a level gauge 302 and a temperature gauge 304 which automatically instruct the bridge by appropriate electrical signals when the hydraulic fluid level is too high or too low or when the hydraulic fluid temperature is excessively high. Drain valve 306 is used to drain reservoir 300 when required. Shut-off valve 308 controls the flow of hydraulic fluid between reservoir 300 and variable volume pumps 310 and 312. The inlets to variable volume pumps 310 and 312 are protected by hydraulic fluid filters 314 and 316, respectively. Pumps 310 and 312 are driven from common electric motor 318.

The variable volume pumps are typically pressure compensated, axial hydraulic piston pumps. Axial hydraulic piston pumps contain a number of reciprocating pistons whose control ends are attached to a wobble plate. The wobble plate can be tilted to vary the quantity of fluid displaced by the pumps. The tilt of the wobble plate can be varied by using a servo valve or by other means which are conventional in the art. The variable volume pumps are isolated by internal check valves so that if one fails the other will keep operating to supply one-half of the capacity of the dual pumps. Although two variable volume pumps are illustrated for operating the starboard fin, it should be understood that only one pump is actually required and that two pumps are provided merely as a safety precaution to insure continued and reliable operation of the hydraulic actuators. Variable dilivery pumps 310 and 312 can be replaced by constant-delivery pumps of proper capacity.

The output from variable volume pumps 310 and 312 is monitored by hydraulic fluid pressure guage 320. Shut-off valve 322 controls the flow of hydraulic fluid from pumps 310 and 312 to and from accumulator 324. Accumulator 324 is illustrated as the hydropneumatic type but can be of mechanical design if desired in which a weighted member or spring is used to apply force to the hydraulic fluid. Accumulator 324 is used as an auxiliary power source to supplement pumps 310 and 312 for peak requirements and therefore assures fast peak response time. Accumulator 324 can also be used to store hydraulic fluid during periods of time in which the hydraulic actuators are not used. Accumulator 324 is also used as an emergency power source in case of power failure. The pressure in accumulator 324 is monitored by hydraulic pressure guage 328. The accumulator is drained by closing shut-off valve 322 and opening drain valve 330 thus returning the hydraulic fluid stored in the accumulator to reservoir 300.

Relief valve 332 acts to limit the system pressure and functions to direct the output from pumps 310 and 312 to reservoir 300 when a safe working pressure is exceeded. Relief valve 332 can be directly opened or pilot-operated and can be of any conventional type. The hydraulic fluid is further filtered by fine filter 334 after it leaves variable volume pumps 310 and 312.

As previously stated, only the hydraulic circuitry for the starboard fin is shown in FIG. 11. If a malfunction occurs in the hydraulic fluid supply system for either the starboard or port fins, both systems can be operated from one or the other of the two sets of variable volume pumps and associated electric motors. This is accomplished by opening shut-off valve 336 and supplying the port side fin hydraulic actuators with hydraulic fluid from starboard fin pumps 310 and 312, or by opening shut-off valve 336 and supplying the starboard fin hydraulic actuators with hydraulic fluid from the port side fin pumps. Normally, however, shut-off valve 336 is closed so that hydraulic fluid does not pass back and forth between the starboard and port side fin hydraulic circuits.

Actuation of hydraulic motor 44 to cause fin extension or retraction is accomplished as follows. Hydraulic fluid is directed to pilot-operated valve 340. Valve 340 is a two position, four-way valve which has one external port plugged. Variable valve 338 controls the volume of hydraulic fluid supplied through valve 340 to hydraulic motor 44 and can be used to trim the speed of hydraulic motor 44 and to control the speed at which fin retraction shaft 40 rotates. Value 340 is operated by pilot value 342. Pilot value 342 is a spring offset, mechanically operated four-way valve which has two positions. Pilot valve 342 is illustrated in the mechanically actuated position. As previously described, cam 343 actuates valve 342 by camming action when the fin is in the non-tilted and substantially horizontal position and ready to be extended or retracted. Cam 343 and arm 343 of pilot valve 342 are shown schematically in the figure.

Hydraulic fluid is supplied to pilot valve 342 by line 344. If pilot valve 342 is in the spring offset position by virtue of the stabilizing fin being in a tilted position, hydraulic fluid is passed by pilot valve 342 into line 346 and forces pilot-operated valve 340 to the left. Pilot fluid from the previous position change of valve 340 returns through line 348 to pilot valve 342 where it is directed into line 350 and thereafter returns to reservoir 300. If pilot valve 342 is in the cam actuated position by virtue of the starboard fin being in the non-tilted and substantially horizontal position and ready for fin extension or retraction, hydraulic fluid from line 344 is directed by pilot valve 342 into line 348 and drives pilot-operated valve 340 to the right. Pilot fluid from the previous position change of valve 340 is forced through line 246 to pilot valve 342 where it is directed into line 350 and returned to reservoir 300.

Pilot operated valve 340 is in the position shown in FIG. 11 when pilot valve 342 is cam offset and the starboard fin is in the not-tilted positon ready to be extended or retracted. In this position, hydraulic fluid is directed by pilot-operated valve 340 to solenoidoperated valve 352 via line 354. Pilot valve 342 is in the spring offset position when the valve 342 is in the spring offset position, pilot-operated valve 340 is forced to the left and the flow of inlet hydraulic fluid through valve 340 is blocked by the plugged external port so that no hydraulic fluid passes through valve 340 into line 354. Accordingly, solenoid-operated valve 352 only receives hydraulic fluid when the starboard fin is in the non-tilted and substantially horizontal position ready for fin extension or retraction.

Solenoid-operated valve 352 is a two stage, three position, four-way valve which is spring centered. Three of the valves ports are interconnected and one port is blocked at neutral. Valve 352 has a manual override so that it can be operated manually during an emergency loss of power. When the solenoids are de-energized and valve 352 is in the spring centered neutral positon, the flow of inlet hydraulic fluid through valve 352 is blocked. When fin extension solenoid 351 is energized and valve 352 is driven to the right, hydraulic fluid from line 354 is passed by valve 352 into line 356. Hydraulic fluid from line 356 actuates hydraulic motor 44 which in turn rotates fin retraction shaft 40 and extends stabilizing fin 30. Hydraulic fluid from hydraulic motor 44 is returned to reservoir 300 via line 358 and valve 352. When fin retraction solenoid 353 is energized, valve 352 is driven to the left and hydraulic fluid is passed by valve 352 into line 358 and then to hydraulic motor 44. Hydraulic motor 44 in turn causes fin retraction shaft-40 to rotate in the opposite direction causing stabilizing fin 30 to retract and hydraulic fluid is returned to reservoir 300 via line 356 and valve 352.

Variable volume pumps 310 and 312 also supply hydraulic fluid to pilot-operated valve 360. Pilot-operated valve 360 is a two position, four-way valve which has one external port plugged. The two positions of valve 360 are controlled by pilot valve 362. Pilot valve 362 is a spring offset, mechanically operated four-way valve which has two positions. As previously described, actuator arm 260 actuates valve '362 by camming action when stabilizing fin 30 is in the fully extended position and ready to be tilted. Pilot valve 362 is shown in its spring offset position. Hydraulic fluid is supplied to pilot valve 362 by variable volume pumps 310 and 312 through line 364. When pilot valve 362 is in its spring offset position, hydraulic fluid is directed by valve 362 into line 366. Pilot fluid in line 366 drives pilotoperated valve 360 to the left. Pilot fluid from the previous position change of valve 360 is forced through line 368 to pilot valve 362 where it is returned to reservoir 300 through line 370. When pilot valve 362 is in the cam offset position, hydraulic fluid from line 364 is directed by valve 362 into line 368. The hydraulic fluid in line 368 forces pilot-operated valve 360 to the right. Pilot fluid from the previous position change is returned through line 366 to reservoir 300 via pilot valve 362.

Pilot valve 362 is only in the cam offset position when the stabilizing fin is fully extended. Otherwise, pilot valve 362 is in the spring offset position. When pilot valve 362 is in the spring offset position and the stabilizing fin is either fully retracted or only partially extended, pilot-operated valve 360 is moved to the left and the flow of hydraulic fluid through the valve is blocked. When pilot valve 362 is in the cam offset position when the stabilizing fin is in the fully extended position, hydraulic fluid can pass through pilot-operated valve 360 to servo valve 372 via line 374. Accordngly, servo valve 372 is only supplied with hydraulic fluid when the stabilizing fin is in the fully extended position.

The novel servo valve of the present invention can be used as servo valve 372 or this valve can be any electrohydraulic servo valve conventionally used to control a hydraulic actuator. Servo valve 372 is connected to reciprocating torque actuator 58 by lines 374 and 376. Stabilizing fin 30 is tilted in one direction if hydraulic fluid is directed by servo valve 372 through line 374 and is tilted in the opposite direction if the hydraulic fluid is directed through line 376. Hydraulic fluid is returned to servo valve 372 through line 376 if line 374 contains the pressurized fluid and is returned through line 374 ifline 376 contains the pressurized fluid. In the hydraulic system illustrated in FIG. 11, servo valve 372 does not have a mechanical feedback linkage between the pilot and main spool in order to close off the control pressure at a point which satisfies the input current command and accordingly a feedback potentiometer 378 whose function has been previously described is shown attached to reciprocating torque actuator 58.

Shut-off valve 380 is used to connect lines 374 and 376 in the case of an emergency loss of power and drain the hydraulic fluid from reciprocating torque actuator 58 to keep the actuator from being locked in a tilted position. Valve 382 can also be employed during an emergency loss of power. Valve 382 is a mechanically operated, two stage, three position, four-way valve. Three of the valves ports are interconnected and one port is blocked at neutral. When valve 382 is in its normal neutral position, the flow of inlet hydraulic fluid through valve 382 is blocked. When valve 382 is me chanically moved to the left, hydraulic fluid can pass through check valve 384 and into line 374 and will also open check valve 386. Accordingly, hydraulic fluid can return to reservoir 300 from reciprocating torque actuator 58 through check valve 386 and valve 382. When valve 382 is mechanically moved to the right, hydraulic fluid can pass through check valve 386 and into line 376 and will also open check valve 384. Accordingly, hydraulic fluid can return to reservoir 300 from reciprocating torque actuator 58 through check valve 384 and and valve 382. Check valves 384 and 386 are pilotoperated by pressurized fluid and keep hydraulic fluid from flowing to valve 382 and from lines 374 and 376 except when opened by pressurized fluid supplied from valve 382.

During an emergency loss of power, valve 382 is supplied with hydraulic fluid stored in accumulator 324 or supplied to accumulator 324 by a small auxiliary hydraulic fluid supply system not shown. Accordingly, valve 382 can be used to move stabilizing fin 30 into its not-tilted position ready for fin retraction if a power loss occurs when stabilizing fin 30 is tilted. In the same manner, the manual override of valve 352 can be used to operate hydraulic motor 44 with hydraulic fluid from accumulator 324.

The over-all operation of the hydraulic system for operating the starboard fin will not be described. For the purposes of description it will be assumed that the starboard fin is in the non-tilted and substantially horizontal position and is fully retracted. Accordingly, pilot valve 342 is in the cam offset position. In this position, hydraulic fluid passes through line 344 and into line 348 via pilot valve 342. Pilot-operated valve 340 is therefore driven to the right and hydraulic fluid is passed into line 354 by valve 340. When the roll of the ship reaches an unacceptable level, fin extension 351 solenoid is energized by captain. Accordingly, hydraulic fluid is passed by solenoid-operated valve 352 into line 356 causing hydraulic motor 344 to rotate fin retraction shaft 40 and extend stabilizing fin 30. Hydraulic fluid is returned to reservoir 300 through line 358 via solenoid-operated valve 352. When stabilizing fin 30 is fully extended, solenoid 351 is tie-energized and valve 352 returned to its neutral position by the centering springs. In this position the flow of hydraulic fluid through solenoid-operated valve 352 is blocked.

Once stabilizing fin 30 has reached its fully extended position, pilot valve 362 is moved from its spring offset position to its cam offset position. In the cam offset position, inlet hydraulic fluid is supplied by pilot valve 362 to line 368. Hydraulic fluid in line 368 drives pilotoperated valve 360 to the right and hydraulic fluid is passed by valve 360 to servo valve 372. On command from gyro command 280, servo valve 372 supplies hydraulic fluid either through line 374 or line 376 to reciprocating torque actuator 58 depending upon the direction of rotation of stabilizing fin 30 that is desired. When the stabilizing fin has been tilted to the desired position to produce the required stabilizing moment, a mechanical or electrical feedback linkage instructs the servo valve 372 to cut off the supply of hydraulic fluid to reciprocating torque actuator 58. This cycle is then repeated in the opposite direction, or as further tilting of the stabilizing fin is required.

While the stabilizing fin is in the tilted position, pilot valve 342 will be in the spring offset position. In this spring offset position, hydraulic fluid from inlet line 344 will be directed into line 346 by pilot valve 342, pilot-operated valve 340 will be moved to the left and the flow of hydraulic fluid through pilot-operated valve 340 will be blocked. Accordingly, no pressurized fluid will be present in line 354 and solenoid-operated valve 352 will be incapable of actuating hydraulic motor 344 because of a lack of inlet pressurized hydraulic fluid from line 354.

When the roll of the ship has again reached an acceptable level, the starboard fin is returned to its nontilted position by servo valve 372. In this position, pilot valve 342 will be in its cam offset position and hydraulic fluid will be directed through pilot valve 342 to move pilot-operated valve 340 to the right. In this position, pilot-operated valve 340 will direct inlet hydraulic fluid from pumps 310 and 312 to solenoid-operated valve 352 through line 354. Solenoid 353 will then be energized and valve 352 will be driven to the left. In this position, inlet hydraulic fluid from line 354 will be passed by valve 352 into line 358 and hydraulic motor 44 will cause fin retraction shaft 40 to rotate in the opposite direction and retract stabilizing fin 30.

As soon as the stabilizing fin has left its fully extended position, pilot valve 362 will assume its spring offset postion. Accordingly, inlet hydraulic fluid to pilot valve 362 will be directed to line 366 and pilot-operated valve 360 will be driven to the left whereby the supply of hydraulic fluid to servo valve 372 will be cut-off. In this position it will be impossible to tilt stabilizing fin 30 since there will be no supply of hydraulic fluid to servo valve 372.

When the stabilizing fin has reached its fully retracted position, solenoid 353 is de-energized and valve 352 reassumes its neutral position. Accordingly, the supply of hydraulic fluid is blocked at solenoidoperated valve 352 and no pressurized fluid is available to actuate hydraulic motor 44.

The servo valve of the present invention is shown in FIG. 12. This valve can be used as servo valve 372 used to control the flow of hydraulic fluid to reciprocating torque actuator 58 in the hydraulic fluid supply system shown in FIG. 11 for operating stabilizing fin 30 of the present invention. The servo valve of the present invention can also be used to control flow to and from other conventional hydraulic actuators, or to control the volume output of a variable volume pump or any other conventional application.

The hydraulic servo valve of the present invention is used for varying working fluid output flow in response to an input control signal. The valve comprises a main spool housing 400. Main spool housing 400 includes center body 402 which is rectangualar in shape as illustrated and has a longitudinal cylindrically shaped opening therein. End caps 404 are attached to main spool housing center body 402 by bolts (not shown) and sealed against external leakage by O-rings 406. Together center body 402 and end caps 404 define main spool chamber 408.

Main spool housing 400 contains working fluid inlet port 410 for supplying hydraulic fluid to main spool chamber 408 from a working fluid reservoir such as reservoir 300 in FIG. 11. Main spool housing 400 also contains working fluid return ports 412 and 414 for withdrawing working fluid from main spool chamber 408, after which the working fluid is directed to a working fluid reservoir. Working fluid transfer port 416 and 418 in main spool housing 400 are used to transfer working fluid between main spool chamber 408 and a hydraulic actuator, variable volume pump or some other hydraulic power response source.

Main spool 420 is positioned in main spool chamber 408. Main spool 420 includes ridges 422, 424, 426, and 428. Lands 430 are in sliding and essentially fluid-tight contact with the walls of main spool chamber 408. Ridges 424 and 426 of main spool 420 are positioned over and close working fluid transfer ports 416 and 418 when main spool 420 is in the null position. Adjacent ridges 424 and 426 of main spool 420 lie on either side of working fluid inlet port 410 and define a working fluid inlet chamber 432. This chamber is continuously supplied with hydraulic fluid from working fluid inlet port 410 when the servo valve is in operation. Adjacent ridges 422 and 424 of main spool 420 lie on either side of working fluid return port 412 when main spool 420 is in the null position. In like manner, adjacent ridges 426 and 428 of main spool 420 lie on either side of working fluid return port 414 when main spool 420 is in the null position.

Centering springs 434 and 436 are of equal resiliency and keep main spool 420 centered in main spool chamber 408 and ridges 424 and 426 blocking working fluid transfer ports 416 and 418 when main spool 420 is in the null position. Cylindrical opening 438 in end cap 402 and cylindrical opening 440 in ridge 422 of main spool 420 act as spring retainer housing for centering spring 434. In like manner, cylindrical opening 442 in end cap 405 and cylindrical opening 444 in ridge 428 of the main spool 420 act as spring retainer housings for centering spring 426. Centering spring chamber 446 is formed between ridge 422 of main spool 420 and end cap 404-of main spool housing 400. In like manner, centering spring chamber 448 is formed between ridge 428 of main spool 420 and end cap 405 of main spool housing 400. Centering spring chambers 446 and 448 contain pilot fluid when the servo valve is in operation' The servo valve also includes pilot housing 450 which has a longitudinal cylindrically shaped pilot sleeve chamber 452 formed therein. Pilot fluid inlet port 454 is formed in pilot housing 450 and acts to supply pilot fluid to pilot sleeve chamber 452 from a pilot fluid reservoir. Pilot fluid return ports 456 and 458 are formed in pilot housing 450 and are used to withdraw pilot fluid from pilot sleeve 452 to a pilot fluid reservoir. Pilot fluid transfer ports 460 and 462 are formed in pilot housing 450 and are used to transfer pilot fluid between pilot sleeve chamber 452 and main spool housing 400. Pilot housing 450 has annular grooves 464, 466, 468, 470 and 472 formed therein in the wall of pilot sleeve chamber 452. Annular grooves 464 and 472 are in fluid communication with pilot fluid return ports 456 and 458, respectively. Annular groove 468 is in fluid communication with pilot fluid inlet port 454. Annular grooves 466 and 470 are in like manner in communication with pilot fluid transfer ports 460 and 462, respectively.

Pilot sleeve 474 is positioned in pilot sleeve chamber 452. Pilot sleeve 474 is cylindrical in shape and its outer surface is in sliding and essentially fluid-tight contact with the surface of pilot sleeve chamber 452. Pilot sleeve 474 has a longitudinal, cylindrically shaped opening extending therethrough which forms pilot spool chamber 476. Pilot sleeve 474 has annular transfer ports 478, 480, 482, 484, and 486 formed therein for transferring pilot fluid between pilot housing 450 and pilot spool chamber 476. Pilot sleeve transfer ports 478, 480, 482, 484, and 486 are in fluid communication with annular grooves 464, 466, 468, 470, and 472, respectively.

Pilot spool 488 is positioned in pilot spool chamber 476 in pilot sleeve 474. Pilot spool 488 comprises ridges 490, 492, 494, and 496 which are in sliding and essentially fluid-tight contact with the walls of pilot spool chamber 476. Adjacent ridges 492 and 494 of pilot spool 488 lie on either side of pilot sleeve transfer port 482 and form pilot fluid inlet chamber 498. Pilot fluid inlet chamber 498 is constantly filled with pressurized hydraulic fluid when the servo valve is in operation. In like manner, adjacent ridges 490 and 492 of pilot spool 488 form pilot fluid return chamber 500 and adjacent ridges 494 and 496 form pilot fluid return chamber 502. Pilot fluid return chambers 500 and 502 are continually in fluid contact with pilot slide transfer ports 478 and 486, respectively. Adjacent ridges 492 and 494 of pilot spool 488 close pilot slide transfer ports 480 and 484 which are used for transferring pilot fluid between pilot housing 450 and pilot spool chamber 476 when pilot spool 488 is in the null position.

The input electrical signal to the servo valve from the gyro or other electrical control source is converted into mechanical motion to move the pilot spool by conventional technique such as by an electromagnetic torque motor which is used to stroke the pilot spool. This means for moving the pilot spool in response to an input control signal is conventional and is not shown in the figures but is rather represented schematically. The movement of pilot spool 488 in response to an input control signal at least partially opens the pilot fluid transfer ports 480 and 484 in pilot spool slide 474 as will be described more fully below.

Main spool chamber transfer lines 504 and 506 are used to transfer pilot fluid from pilot housing 450 to main spool chamber 408 to thereby move main spool 420 and at least partially open working fluid transfer ports 416 and 418 to transfer working fluid between main spool chamber 408 and the hydraulic power response source via working fluid transfer lines 508 and 510, respectively. The hydraulic power response source is represented as a hydraulic reciprocating torque actuator in the figure.

The reciprocating torque actuator generally comprises a housing 512, a vane 514 and a drive shaft 516. Vane 514 divides the interior of the actuator into chambers 518 and 519. When hydraulic fluid is introduced into chamber 518 or 519 shaft 516 is caused to rotate in either a clockwise or counterclockwise direction depending upon which chamber the hydraulic pressurized fluid is introduced. Attached to shaft 516 of the reciprocating torque actuator at a suitable point off center of the shaft is bell crank 520. Attached to the opposite end of bell crank 520 is feedback linkage 522 which is connected to bolt 524. Bolt 524 is threaded into threaded end 526 of pilot sleeve 474 and is retained in place by locking nut 528. Air vent 530 communicates with air cavity 532 formed between the end of bolt 524 and the end of ridge 490 of pilot spool 488. Air vent 530 exhausts air cavity 532 and prevents air pressure from building up in air cavity 532 due to the reciprocation of pilot spool 488. Bolt 524 can be threaded into or unthreaded from pilot sleeve 474 to vary the null position location of pilot sleeve 474.

Bell crank 520, feedback linkage 522 and bolt 524 all cooperate to move the pilot sleeve in response to the hydraulic actuator and close the pilot sleeve transfer ports 480 and 484 after a desired response from the hydraulic actuator has been obtained.

The servo valve of the present invention functions as follows to vary working fluid output flow in response to an input control signal from a gyro or the like. Hydraulic fluid is introduced under pressure into working fluid inlet chamber 432 through working fluid inlet port 410. At this point, main spool 420 is in the null position and is centered in main spool chamber 408 by centering springs 434 and 436. Pilot hydraulic fluid is introduced under pressure into pilot fluid inlet chamber 498 through pilot fluid inlet port 454 and annular groove 468 in pilot housing 450 and transfer port 482 in pilot sleeve 474. The pilot fluid pressure is evenly distributed on the inside faces of ridges 492 and 494 of pilot spool 488. Pilot spool 488 remains in the null positionwith ridges 492 and 494 blocking pilot sleeve transfer ports 478 and 484.

The input electrical signal is converted into mechani cal motion by conventional means such as an electromagnetic torque motor and pilot spool 488 is caused to move longitudinally to the right or to the left depending upon the input control signal. For the purposes of description, it will be assumed that the pilot spool 488 is slid to the left by the input signal thereby at least partially uncovering pilot sleeve transfer ports 480 and 484. Pilot fluid flows out of pilot fluid inlet chamber 498 through pilot sleeve transfer port 480, into annular groove 466, into pilot housing transfer port 460,

through pilot fluid transfer line 504 in main spool housing 400 and into centering spring chamber 446.. The increased pressure of the pilot fluid acting to the right on main spool 420 upsets the balance of main spool 420 caused main spool 420 to move from its null position to the right thereby partially opening working fluid transfer ports 416 and 418 in main spool housing 400.

Working fluid passes from working fluid inlet'chamher 432 through partially unblocked working fluid transfer port 418, through working fluid transfer line 510 and into chamber 518 of the reciprocating torque actuator on the right side of vane 514. Accordingly, vane 514 and shaft 516 of the reciprocating torque actuator are caused to move in a clockwise direction. The clockwise movement of shaft 516 causes the end of hell crank 520 attached to shaft 516 to move downward and feedback linkage 522 to move to the left. Feedback linkage 522 in turn moves bolt 524 and pilot sleeve 474 to the left.

Vane 514 and shaft 516 of the reciprocating torque actuator continue to move in a clockwise direction until pilot sleeve 474 has been moved to the left suffi- 

1. A device for damping the rolling motion of a ship comprising a fin chamber adapted to be located arthwartship in a ship''s hull, a fin support axle having an opening therein slidably mounted in the fit chamber, a stabilizing fin rotatably mounted on the fin support axle and adapted to be located arthwartship in the operative position on one side of the ship''s hull below the water line, a fin retraction shaft having a threaded section being rotatably mounted in the fin chamber and extending into the opening in the fin support axle, rotation means rotatably engaging the fin retraction shaft, nut means mounted in the opening of the fin support axle and operatively engaging the threaded section of the fin retraction shaft such that the stabilizing fin moves arthwartship when the fin retraction shaft is rotated and means cooperating with the stabilizing fin for rotating the stabilizing fin on the fin support axle.
 2. The device of claim 1 in which the outboard end of the fin retraction shaft carries retaining means rotatably engaging the walls of the central opening in the fin support axle.
 3. The device of claim 2 in which the opening in the fin support axle extends completely therethrough and the nut means and retaining means are lubricated by water.
 4. A device for dampling the rolling motion of a ship and which extends and stows athwartship comprising a fin chamber adapted to be located athwartship in a ship''s hull, a fin support axle slidably mounted in the fin chamber, a stabilizing fin rotatably mounted on the fin support axle and adapted to be located arthwartship in the operative position on one side of the ship''s hull below the water line, a fin retraction shaft having a threaded section extending arthwartship in the fin chamber and being rotatably mounted to the fin chamber, the fin retraction shaft bein non-movable in the arthwartship direction, rotation means located outside the fin chamber and adapted to be located in the ship''s hull rotatably engaging the fin retraction shaft, nut means fixedly mounted to the fin support axle and operatively engaging the threaded section of the fin retraction shaft such that the stabilizing fin moves athwartship when the fin retraction shaft is rotated, a fin tilting shaft extending athwartship in the fin chamber and being rotatably mounted to the fin chamber, rotation means located oustide the fin chamber and adapted to be located in the ship''s hull rotatably engaging the fin tilting shaft, cam means rotatably engaging the fin tilting shaft, and a fin tilting arm attached to the stabilizing fin and engaging the cam means such that the stabilizing fin rotates on the fin support axle when the cam means is rotated by the fin tilting shaft.
 5. The device of claim 4 in which the fin support axle is slidably mounted in the fin chamber by means of inboard and outboard sliding shoe mounts.
 6. The device of claim 5 in which the inboard and outboard sliding shoe mounts are slidably mounted on guiderails extending athWartship in the fin chamber.
 7. The device of claim 4 in which the stabilizing fin is rotatably mounted on journal bearings attached to the fin support axle.
 8. The devide of claim 7 in shich the stabilizing fin is rotatably mounted on the fin support shaft by means of radial bearings engaging the journal bearings carried by the fin support axle.
 9. The device of claim 8 in which the radial bearings rotatably mounting the stabilizing fin on the fin support axle are lubricated by water.
 10. The device of claim 4 in which the fin retraction shaft and the fin tilting shaft are rotatably mounted to the fin chamber by means of radial bearings.
 11. The device of claim 10 in which the radial bearings rotatably mounting the fin retraction shaft and the fin tilting shaft to the fin chamber are lubricated by water.
 12. The device of claim 4 in which the cam means comprises a cylindrical sleeve which is rotatably mounted on the fin support axle and which rotatably engages the fin tilting shaft and a cam arm which engages the fin tilting arm.
 13. The device of claim 12 in which the cylindrical sleeve of the cam means is rotatably mounted on the fin support axle and rotatably engages the fin tilting shaft by means of bearings which are lubricated by water.
 14. The device of claim 12 in which the cam arm has a pin attached to one of its faces.
 15. The device of claim 14 in which the fin tilting arm is bifurcated and in which the slot formed by the two branching members of the bifurcated fin tilting arm alidingly engages the pin attached to the cam arm.
 16. The device of claim 4 and further comprising a tail flap pivotally attached to the stabilizing fin.
 17. The device of claim 16 and further comprising a fixed pin attached to the fin support axle and a tail flap tilting arm attached to the tail flap and engaging the fixed pin such that the tail flap rotates about the fixed pin when the stabilizing fin is rotated by the cam means.
 18. The device of claim 17 in which the tail flap tilting arm is bifurcated and in which the slot formed by the two branching members of the bifurcated tail flap tilting arm slidingly engages the fixed pin attached to the fin support axle.
 19. The device of claim 4 and further comprising a male locking member mounted on the fin chamber and a female locking member mounted on the fin support shaft, the male locking member mating with the female locking member when the stabilizing fin is in its fully retracted position such that the stabilizing fin can be locked against extension.
 20. The device of claim 4 and further comprising means for determining the position of the stabilizing fin in the fin chamber.
 21. A device for damping the rolling motion of a ship and which extends and stows athwartship comprising a fin chamber adapted to be located athwartship in a ship''s hull, a fin support axle having a central opening therein slidably mounted in the fin chamber, a stabilizing fin rotatably mounted on the fin support axle and adapted to be located athwartship in the operative position on one side of the ship''s hull below the water line, a fin retraction shaft having an external screw thread on its outboard end being rotatably mounted to the fin chamber and extending into the central opening in the fin support axle, the fin retraction shaft being non-movable in the athwartship direction, retaining means mounted on the outboard end of the fin retraction shaft slidably and rotatably engaging the walls of the central opening in the film support axle, rotation means located outside the fin chamber and adapted to be located in the ship''s hull rotatably engaging the fin retraction shaft, nut means fixedly mounted in the central opening of the fin support axle having an internal screw thread and operatively engaging the screw thread of the fin retraction shaft such that the stabilizing fin moves athwartship when the fin retraction shaft is rotated, a fin tilting shaft extending athwartship in the fin chamber and being rotatabLy mounted to the fin chamber, rotatation means located outside the fin chamber and adapted to be located in the ship''s hull rotatably engaging the fin tilting shaft, cam means having a pin fixedly attached to its outboard face rotatably mounted on the fin support axle and rotatably engaging the fin tilting shaft, and bifurcated fin tilting arm attached to the stabilzing fin and having the slot formed by its two branching members slidingly engaging the pin attached to the cam means such that the stabilizing fin rotates on the fin support axle when the cam means is rotated by the fin tilting shaft.
 22. The device of claim 21 in which the retaining device interacts with the nut means to prevent the fin retraction shaft from being disengaged from the nut means when the stabilizing fin is fully extended.
 23. The device of claim 21 in which the retaining device functions to prevent the fin retraction shaft from flexing as the stabilizing fin is retracted.
 24. In a device for damping the rolling motion of a ship in which a stabilizing fin adapted to be located athwartship in the operative position on one side of the ship''s hull below the water line is mounted in a fin chamber and in which a drive shaft for the stabilizing fin is driven by a drive shaft of a prime mover located in the ship''s hull, the improvement comprising a mounting plate mounted to the stern of the fin chamber and having an opening therein through which the drive shaft for the stabilizing fin extends, gland means mounted in the opening of the mounting plate and surrounding the drive shaft of the stabilizing fin, bearing means for mounting the drive shaft of the stabilizing fin to the fin chamber and seal means for sealing off the inside of the ship''s hull from the inside of the chamber housed in said gland means, and a coupling housing mounted to the gland means surrounding the drive shaft of the stabilizing fin and attaching the prime mover for the stabilizing fin directly to the fin chamber and aligning the longitudinal axis of the drive shaft of the prime mover with the longitudinal axis of the drive shaft for the stabilizing fin.
 25. The improved device of claim 24 in which the gland means comprises a mounting housing extending into the opening in the mounting plate and having an opening therein through which the drive shaft of the stabilizing fin extends and a gland housing extending into the opening in the mounting housing and housing the bearing and sealing means.
 26. The improved device of claim 25 including a retaining nut threaded to the gland housing and cooperating with the seal means to increase the seal between the gland housing and the drive shaft for the stabilizing fin.
 27. The improved device of claim 25 in which the seal and bearing means abut against a radially extending shoulder of the gland housing.
 28. The improved device of claim 24 including a coupling for coupling the drive shaft for the stabilizing fin to the drive shaft of the prime mover housed in the coupling housing.
 29. The improved device of claim 24 in which the coupling housing comprises a unitary metal casting.
 30. The improved device of claim 24 including bearing means for transmitting longitudinal forces in the drive shaft for the stabilizing fin to the coupling in the coupling housing.
 31. A device for damping the rolling motion of a ship comprising a fin chamber adapted to be located athwartship in a ship''s hull, a fin support axle having an opening therein slidably mounted in the fin chamber, a stabilizing fin mounted on the fin support axle and adapted to be located athwartship in the operative position on one side of a ship''s hull below the water line, a fin retraction shaft extending into the opening in the fin support axle, means mounted to the fin retraction shaft comprising roller means rotatably engaging the walls of the opening in the fin support axle and bearing means separating the roller means from the fin retraction shaft, and rotation means rotatably engaging the fin Retraction shaft.
 32. The device of claim 31 in which the roller means is a cylindrical metal roller.
 33. The device of claim 31 in which the bearing means are lubricated by water.
 34. The device of claim 31 in which the bearing means comprise two cylindrical bearings which are L-shaped in crosssection and which have radial flanges in abutting relationship with the ends of the roller means.
 35. In a device for damping the rolling motion of a ship in which a stabilizing fin adapted to be located athwartship in the operative position on one side of the ship''s hull below the water line is fitted to the ship and in which the extension, retraction and tilting of the stabilizing fin are controlled by hydraulic actuators, the improvement comprising a hydraulic system for controlling the extension, retraction and tilting of the stabilizing fin including a first hydraulic actuator for extending and retracting the stabilizing fin, a second hydraulic actuator for tilting the stabilizing fin, means for supplying hydraulic fluid to the first and second hydraulic actuators, first valve means for controlling the supply of hydraulic fluid to the first hydraulic actuator in response to a control signal to thereby extend and retract the stabilizing fin, second valve means for supplying the first valve means with hydraulic fluid only when the stabilizing fin is properly positioned for fin extension and retraction, servo valve means for supplying the second hydraulic actuator with hydraulic fluid in response to a control signal to thereby tilt the stabilizing fin in a controlled direction, and third valve means for supplying hydraulic fluid to the servo valve means only when the stabilizing fin is in the fully extended position.
 36. The improved hydraulic system of claim 35 in which the second valve means includes pilot-operated valve means for supplying hydraulic fluid to the first valve means only when in a first position and pilot valve means cooperating with the stabilizing fin to move the pilot-operated valve means to the first position only when the stabilizing fin is in a position ready to be extended and retracted.
 37. The improved hydraulic system of claim 35 in which the third valve means includes a pilot-operated valve means in which hydraulic fluid is supplied to the servo valve means only when the pilot-operated valve means is in a first position and a pilot valve cooperating with the stabilizing fin for moving the pilot-operated valve means to the first position only when the stabilizing fin is in its fully extended position.
 38. The improved hydraulic system of claim 35 in which the first valve means is a three position, solenoid-operated valve in which the flow of hydraulic fluid through the first hydraulic actuator is blocked when the valve is in its neutral position.
 39. The improved hydraulic system of claim 35 in which the means for supplying hydraulic fluid includes a motor and a variable volume pump driven by the motor.
 40. In a device for damping the rolling motion of a ship in which a stabilizing fin adapted to be located athwartship in the operative position on one side of the ship''s hull below the water line is fitted to the ship and in which the extension, retraction and tilting of the stabilizing fin are controlled by hydraulic actuators, the improvement comprising: a hydraulic system for controlling the extension, retraction, and tilting of the stabilizing fin including a first hydraulic actuator for extending and retracting the stabilizing fin; a second hydraulic actuator for tilting the stabilizing fin; means for supplying hydraulic fluid to the first and second hydraulic actuators; solenoid-operated valve means for controlling the supply of hydraulic fluid to the first hydraulic actuator, said solenoid-operated valve means being a two stage, three position valve in which the first hydraulic actuator is caused to extend the stabilizing fin when the solenoid-operated valve is in the first position, the first hydraulic actuatoR is caused to retract the stabilizing fin when the solenoid-operated valve is in the second position and in which the flow of hydraulic fluid to the first hydraulic actuator is blocked when the solenoid-operated valve is in the neutral position; first pilot-operated valve means for supplying hydraulic fluid to the solenoid-operated valve means only when the first pilot-operated valve means is in its first position; first pilot valve means mechanically cooperating with the stabilizing fin for moving the first pilot-operated valve means to its first position only when the stabilizing fin is in the proper position for fin extension and retraction; servo valve means for supplying hydraulic fluid to the second hydraulic actuator to tilt the stabilizing fin in response to an input control signal; second pilot-operated valve means for supplying hydraulic fluid to the servo valve means only when the second pilot-operated valve means is in its first position; and second pilot valve means mechanically cooperating with the stabilizing fin for moving the second pilot-operated valve means to its first position only when the stabilizing fin is in its fully extended position.
 41. The improved hydraulic system of claim 40 in which each of the first and second pilot-operated valve means are two position, four-way valves in which one external port is plugged.
 42. The improved hydraulic system of claim 40 in which each of the first and second pilot valve means are two position, four-way valves which are spring offset and mechanically operated.
 43. The improved hydraulic system of claim 40 in which the first pilot valve means moves the first pilot-operated valve means to its first position when the first pilot valve means is mechanically operated.
 44. The hydraulic system of claim 40 in which the second pilot valve means moves the second pilot-operated valve means to its first position when the second pilot valve means is mechanically operated.
 45. The improved hydraulic system of claim 40 including a variable valve for controlling the volume of hydraulic fluid supplied to the first hydraulic actuator.
 46. In a device for damping the rolling motion of a ship in which a stabilizing fin adapted to be located athwartship in the operative position on one side of the ship''s hull below the water line is fitted to the ship and in which the extension and retraction of the stabilizing fin are controlled by a hydraulic actuator, the improvement comprising a system for controlling the extension and retraction of the stabilizing fin including a hydraulic actuator for extending and retracting the stabilizing fin, means for supplying hydraulic fluid to the hydraulic actuator including electrically-operated valve means for controlling the supply of hydraulic fluid to the hydraulic actuator in response to an electric command signal, electrical power source, electrical circuit means connecting the power source with the electrically-operated valve means and limit switch means mechanically operated by the stabilizing fin for conditioning the electrical circuit means such that the electrically-operated valve means is ready to supply hydraulic fluid on command to the hydraulic actuator for fin extension when the stabilizing fin is in the fully retracted position and is ready to supply hydraulic fluid on command to the hydraulic actuator for fin retraction when the stabilizing fin is in the fully extended position, said limit switch means including a first contact having open and closed positions and which is normally open, a second contact having open and closed positions and which is normally closed, and relay means for closing the first contact and opening the second contact when the limit switch is closed.
 47. The improved device of claim 46 in which the electrically-operated valve means for controlling the supply of hydraulic fluid to the hydraulic actuator is a solenoid-operated valve.
 48. The improved device of claim 46 in which the electrical circuit means includes a switch Having a contact having open and closed positions and which is normally open and relay means for closing the contact when the switch is closed.
 49. In a device for damping the rolling motion of a ship in which a stabilizing fin adapted to be located athwartship in the operative position on one side of the ship''s hull below the water line is fitted to the ship and in which tilting of the stabilizing fin is controlled by a prime mover, the improvement comprising a system for controlling the tilting of the stabilizing fin including a prime mover for tilting the stabilizing fin, said prime mover comprising a hydraulic actuator, hydraulic servo valve means for controlling the movement of the prime mover in response to a command signal, means for supplying a command signal to the prime mover to tilt the stabilizing fin, electrical circuit means connecting the command signal supply means and the hydraulic servo valve means for controlling the movement of the prime mover and limit switch means mechanically operated by the stabilizing fin for conditioning the electrical circuit means such that the command signal can only be supplied to the prime mover to tilt the stabilizing fin when the stabilizing fin is properly positioned for fin tilting, said limit switch means including a contact having open and closed positions and which is normally open and relay means for closing the contact when the limit switch is closed.
 50. The improved device of claim 49 in which the means for supplying a command signal to the prime mover to tilt the stabilizing fin is a gyroscope. 